In recent years, lighting technology is rapidly developed, particularly lighting devices adopting the technology of light emitting diodes (LED). Lighting devices provided with LEDs have numerous advantages, such as energy saving, long lifetime, and color control etc., which advantages are much more significant, particularly compared with traditional incandescent lamps and discharge light sources. In order to realize white light utilizing LED technology, a blue LED chip can generally be used in combination with a yellow phosphor and red phosphor or a green phosphor and a red phosphor, so as to mix light to form white light. In order to realize the application of LED technology, the obtainment of a red phosphor used to form white light becomes a key topic.
A technical solution is provided according to the prior art, see, U.S. Pat. No. 7,846,350 B2, which discloses a group of red-emitting phosphors. And the phosphor group consists of Mg14(Ge(5-a)Mna)O24, Sr(Ge(4-b)Mnb)O9Mg2(Ti(1-c)Mnc)O4 etc. In addition, different maximum emission peaks can be realized through the phosphors when being respectively excited by light sources having different wavelengths, e.g., in the system Zn2(Ti(1-d)Mnd)O4, such a phosphor can have an emission peak located at 675 nm under excitation of a light source located at 362 nm. However, These phosphors can not be excited by blue light, especially the blue light at 460-470 nm, and the emission peak locates in the deep red range which is not the most sensitive range to human eyes.
Additionally, with reference to U.S. Patent Publication No. 2006/0169998 A1, it discloses a red phosphor family, which is doped with a tetravalent manganese ion Mn4+, and would have an emission peak located between 600 nm and 642 nm under excitation of a light source having a wavelength between 450 nm and 470 nm. Although the technical solutions can achieve the effect of emitting red light, the stability of the phosphor in a high temperature environment is poor, e.g., the phosphor would decompose at 200° C., and HF acid that is highly toxic is required in the synthesis, which restrains the application of the LED having the phosphor.
In another technical solution of the prior art, an oxynitride red phosphor is provided, and is applied to LED lighting technology. U.S. Pat. No. 8,274,215 B2 discloses a red-emitting phosphor based on CaAlSiN3 type compounds that are activated by Eu2+, and a phosphor of such a type can be excited by blue light and have an emission peak located at 630 nm or 640 nm. In spite of this, the raw materials required by the phosphor and the synthesis process of the nitride compounds require high costs, and a high temperature and high pressure environment is necessary for forming the phosphor.
In addition, U.S. Pat. No. 7,329,371 B2 discloses an oxide phosphor, which can be excited by a light source having a wavelength between 350 nm and 430 nm, and emit red light. However, the phosphor of such a type cannot be excited by a blue light source, and therefore cannot be applied to blue light sources.